Components made of a sintered material comprising a hard phase and a binder phase, are used in a wide range of applications, for example in components subjected to extreme wear under abrasive conditions. In the oil, gas and mining industry it is a commonly used material in several important components, from drilling bits to general wear parts. The most important material properties of such components are a combination of high surface hardness and high toughness. Preferably the outer surface shows a high hardness to combat abrasive wear, and the core of the body shows a high toughness to withstand impact damage.
Cemented carbide is an example of such a material comprising tungsten carbide particles in a binder phase of typically cobalt and/or nickel. The manufacturing typically comprises the steps of mixing and wet milling powders of WC and Co to a slurry, spray draying the slurry and press bodies of the spray dried powder to a desired shape. The pressed bodies are sintered to form dense bodies of cemented carbide. The sintered bodies may, due to dimension tolerances, be ground or machined into its final dimensions.
The surface of a sintered cemented carbide body can be treated by a surface hardening method to improve the wear resistance of the body. Traditionally this surface treatment is applied through for example vibration tumbling, centrifugal tumbling or shot peening. Another example of a surface treatment method is cascading, disclosed in US 2005/0053511 and in US 2010/0075122.
These known surface hardening treatments are based on mechanical impact or deformation of the outer surface of the body, such that a mechanical hardening or work hardening zone forms at and just below the surface. During the deformation, dislocations are moving in the material and new dislocations are formed, and dislocations are locking each other whereby an increase in hardness is achieved.